What Causes the Toilet Tank to Refill Without Flushing?

Normally a toilet's tank will sit silent until you push the handle, flushing the toilet, unless there is a problem with one of several parts inside the tank. Take care when removing the tank cover since it can break readily and is not easily replaced. Do not worry about wearing gloves when dealing with the toilet's tank, though, since none of the toilet's waste water ever enters the tank.

Flapper Valve

A leaking flapper valve in your toilet's tank will allow a trickle or more of water to leave the tank constantly. The trickling of water will eventually drop the water level in the tank to the point that the float in the toilet will trigger the fill valve, which will refill the tank to the level you have set. This will continue over and over until you replace the flapper valve with a new one, which costs little and takes only minutes to install.

Chain Adjustment

Your flapper valve may be in perfect shape, but the small chain that connects the valve to the toilet's handle can cause the tank to refill without you touching the handle. The chain should allow the flapper valve to rest completely over the drain in the bottom of the tank, but it also should not have so much slack that the links bind up. Slide the chain off the clip that attaches it to the handle, and try other links until you find the right setting.

Fill Valve Tube

The fill valve inside the toilet's tank uses a plastic tube, which sends water down the overflow tube in the toilet. The water that goes down the overflow tube makes its way to the toilet bowl, refilling the bowl at the same time the tank refills. The tube can siphon water out of the tank if the tube falls down into the actual overflow tube. Use a clip that holds the tube over the overflow tube's opening, keeping the tube from entering the overflow tube.

Float Adjustment

Toilet floats either sit on the end of a metal arm, or they slide up and down on a metal rod inside the toilet's tank. The float gives feedback to the tank's fill valve about the amount of water in the tank. When the water drops below a certain level, and along with it the float, the fill valve will kick on and bring the water level back up. If the float is adjusted to a level that is too close to the height of the overflow tube's opening, any bump or sloshing of the water can cause the water level to drop and the tank to refill. Bend the float's arm down, or twist the plastic screw on the mechanism to set the float's level lower in the tank.